(1) Field of the Invention:
The present invention relates to a burner of the air adjustment type using a liquid fuel such as methyl alcohol. More particularly, the invention relates to a burner of the air adjustment type in which by changing the amount of air flown into the burner, the heating power can be adjusted in a broad range promptly by many stages, undulation or intermission of flames can be effectively prevented in any stage of the heating power adjustment, the maximum heating power can be uniformalized throughout the burning operation, namely at ignition, during normal combustion and just before exhaustion of the fuel, and incomplete combustion can be effectively prevented in any stage of the burning operation.
In the instant specification and claims, by the term "burner of the air adjustment type" is meant an apparatus in which a substance which is liquid in the normal state but generates a combustible gas at room temperature or under heating is used as a fuel, the heating power generated by gas phase combustion of the combustible gas is adjusted by changing the amount of air fed into the apparatus and the so adjusted heating power is utilized for cooking or the like.
(2) Description of the Prior Art
Burners charged with gaseous, liquid or solid fuels, such as so-called portable ranges, have heretofore been used broadly for outdoor cooking, table cooking and the like. For example, ranges installed with a bomb filled with a liquefied natural gas, a liquefied petroleum gas or the like are used for table cooking and the like, and a heating power necessary and sufficient for table cooking can be supplied by ranges of this type and the heating power can be adjusted smoothly in a broad region. However, ranges of this type have various defects and disadvantages. For example, when the heating power is adjusted to a very low level, flames are often extinguished or during cooking flames are blown off, inviting a risk of explosion or poisoning. Further, since high pressure bombs are used, the fuel cost is increased in ranges of this type, and care must be paid to preservation or discarding of such bombs.
On the other hand, ranges using an alcohol such as methyl alcohol as a fuel are advantageous because blow-off of flames is not caused and they can be used in safety. However, a maximum heating power is very low and hence, they are applicable only to preservation of heat in cooked foods or to cooking of foods having a very small heat capacity. Moreover, the difference between adjustable maximum and minimum heating powers is very small and fine adjustment of the heating power adjustment is very difficult.
A most popular known alcohol range comprises a fuel tank, a gas chamber connected to the upper portion of the fuel tank and a sole combustion gas opening formed on the upper portion of the gas chamber. In this alcohol range, only a flame consisting of a sole solid stream is formed and hence, the heating power is very low. Further, diffusion or dispersion of air in this sole solid stream is very difficult and incomplete combustion is readily caused to occur. Moreover, only a part of a pan bottom is selectively heated and uniform heating is impossible, and adjustment of the heating power is difficult. As a modification of this alcohol range, there is known an alcohol range in which a plurality of variable air openings are formed on the side wall of the gas chamber and the heating power can be adjusted by controlling the degree of opening in these air openings. More specifically, in the range of this type, a primary combustion layer is formed in the boundary between a stream of air flown into the gas chamber from the air openings and a combustible gas filled in the gas chamber, formation of the combustible gas by gasification of the liquid fuel is promoted by transfer of the heat from this combustion layer to the fuel in the fuel tank, and the heating power is adjusted by adjusting the amount of heat in the primary combustion layer by opening or closing the air openings. In this burner of the air adjusting type generating a sole solid stream, as the pressure of the combustible gas filled in the gas chamber becomes high, the amount of air flown into the gas chamber is decreased and it becomes difficult to maintain a sufficient amount of heat in the primary combustion layer. Thus, it is difficult to maintain a sufficient maximum heating power and adjust the heating power in a broad region by many stages. Moreover, the above-mentioned defects inherent in the alcohol range of the sole solid stream type cannot be sufficiently overcome. Still further, in the known burner of the air adjustment type, when completely closed air openings are opened or when the air openings are kept in the slightly opened state, undulation, disturbance or intermission of flames can hardly be prevented, and it is very difficult to obtain a sufficiently high maximum heating power and adjust the heating power through a broad range by many stages. More specifically, in the known burner of the air adjustment type, it is very difficult to obtain a sufficiently high maximum heating power, adjust the heating power through a broad range by many stages and prevent incomplete combustion sufficiently while forming a stable primary combustion layer even at the time of opening the completely closed air openings or in the state where the air openings are slightly opened. As a result, prevention of undulation or intermission of the flame by intermissive primary combustion cannot be attained simultaneously with enhancement of the maximum heating power, multi-staged adjustment of the heating power through a broad range or prevention of incomplete combustion.
As another type of the alcohol range, there is known a burner in which the heating power is adjusted by changing an open area of an annularly disposed core member by the vertical movement of the core member or a covering member. In this burner, however, since the core member or cover member is disposed at a position very close to a high temperature combustion zone, the core member or cover member is excessively heated, and even if the open area of the core member is decreased, generation of the combustible gas is kept vigorous and it is ordinarily difficult to lower the heating power and is often difficult to extinguish the flame. Further, even if the combustible gas forms an annular stream in the opening portion of the core member, by the pressure of air from the peripheral portion of the annular stream a formed flame is caused to take a form of the sole solid stream unless a complicated structure including a central hollow portion thrusting through the entire structure in the vertical direction is adopted. Therefore, incomplete combustion of the combustible gas is readily caused in the interior of the flame. Still further, since the cover member falls in sliding contact with the soft liquid-absorbing core member in the area very close to the high temperature combustion zone, the core member is readily damaged and troubles are brought about by damage to the core member.
As will be apparent from the foregoing illustration, in conventional burners using a fuel which is liquid in the normal state and generates a combustible gas at room temperature or under heating, such as methyl alcohol, there is not known a structure in which the heating power can be promptly adjusted through a broad range in many stages or a structure in which a maximum heating power is uniformly maintained at a level sufficiently applicable to ordinary cooking throughout the burning operation, namely at ignition, during normal combustion and just before exhaustion of the fuel, incomplete combustion can be effectively prevented in any stage of the burning operation and undulation or intermission of flames can be effectively prevented in any heating power adjustment stage.